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Aerial searches for infected Larch across Wales

Specialists from Natural Resources Wales are tracking the spread of a disease affecting Larch trees by conducting helicopter surveys of public and private forests across Wales.

Initial results from a survey earlier this month found the disease (Phytophthora ramorum) may not have spread as widely as in previous years.

Ten new sites have been identified covering approximately 40 hectares (approximately 40,000 trees) of forestry that warrant further investigation.

This is in comparison with results in 2013 which found the disease, which is highly infectious and fatal to larch, had spread to over 3000 hectares, approximately 3 million trees.

The rapid spread of the disease could have been the result of the exceptionally wet summer in 2012, which created the ideal conditions for the spores to spread and infect new trees.

The discovery that the spread of the disease is not as widespread may be the result of the drier summer last year.

Aerial surveys are the best way to spot potential new areas of infection as the larch trees bud or flush during the spring.

It is the first part of the process to identify new areas of infection. These will be followed by further surveying and sampling work on the ground to confirm the presence of the disease.

Under the Welsh Government strategy for tackling the disease, new areas of infection will be targeted quickly to try and slow the spread.

This usually involves felling, but in some areas, Natural Resources Wales is experimenting with a stem injection treatment that kills the trees to stop the spores that spread the disease from being produced.

Since the disease was first identified in Wales in 2010, more than 6000 hectares (14,500 acres) of woodland have become infected, which is roughly around 6 million trees.

More than 2 million Larch trees on the Welsh Government woodland estate have so far been felled with more work planned in areas of Cwmcarn Forest.

The organisation announced recently that Cwmcarn Forest Drive in south Wales will close later this year as approximately 160,000 infected larch trees will need to be felled.

Work is ongoing to replant with different, more varied species like native oak, lime and rowan, as well as more marketable timber like spruce.

This will help create more attractive forests for people to visit and make them more resilient to diseases and climate change.

Of the 3.4 million trees planted in the last 18 months by Natural Resources Wales, 750,000 of these will replace those felled because of the disease.

The replanting is targeted at areas where it will have the maximum benefit for people, the environment and the economy.

Ceri Davies from Natural Resources Wales said:

“These results are encouraging compared to what we found last year but more trees may show signs of infection as they flush later in the year.

“The work we are doing, from the survey work, to felling and replanting, is all aiming to try and slow down the spread of this disease in our larch trees.

“Unfortunately, those trees that are infected will die or be felled, but we are taking the opportunity this gives us to create better, more resilient forests for the future.”